The invention relates to an oscillating displacement pump for liquid or gaseous delivery media, with a delivery space which is delimited on one side by a pump head and on the other side by a delivery element which is drivingly connected to an eccentric drive, an inlet valve with an inlet connection and an outlet valve with an outlet connection being connected to the delivery space, the pump having a pulsation damper at least on the pressure side, and also an excess pressure limiting device between the pressure side and the suction side; in particular, a diaphragm pump with a delivery element formed by a diaphragm.
Diaphragm pumps, which are used as liquid pumps or else as gas pumps, work on the principle of oscillating displacement pumps. This principle naturally causes pulsation on both the suction and the pressure sides. Pulsation on the pressure side in diaphragm pumps, and in particular in fast-running diaphragm pumps, can cause cavitation, pressure peaks, and vibrations.
The harmfulness of cavitation in liquid pumps is known. In addition it causes noise and leads to unstable delivery amounts.
Pressure peaks can damage, or affect the functioning of, devices fitted in the suction conduit. Vibrations cause noise and are transmitted to peripheral devices or to the same device.
In diaphragm pumps, pulsation on the pressure side causes pressure peaks and vibrations. The effects are the same as on the suction side but more radical, since on the pressure side—in contrast to the suction side—the pressure peaks can rise much higher.
With a closed or blocked system, diaphragm liquid pumps compress a liquid until the weakest link in the chain yields. This leads to damage to this element.
From U.S. Pat. No. 2,405,466, a pump of the above-mentioned type is known. This has a suction-side and a pressure-side damper, respectively with a damping chamber filled with air. A disk with one or more apertures, or of porous material, is provided between the damping chamber and respectively the inlet chamber or the outlet chamber. This partially permeable disk between the air filling and the liquid delivery medium in the inlet chamber or respectively the outlet chamber is to prevent the damping air cushion being entrained with the liquid stream.
Such a damping device can only work with the pump used in a position in which the damping chambers are oriented upwardly. Furthermore, the pump is only provided for delivery of liquids, and finally the damping chambers are comparatively quite voluminous for sufficient damping.